In power saving receivers, for example, for medical applications, it is known to employ an ultra low power secondary receiver responsive to a characteristic signal pattern to turn on the primary receiver when there is data to send. Such an exemplary system is described in US2006/0229053A1, the contents of which are herein incorporated by reference. Such a system is typically based on Pulse Amplitude, Pulse Position or Pulse Width Modulation.
As with any kind of Amplitude Modulation technique, the performance is limited by Signal to Noise Ratio (SNR), which affects sensitivity or operational range. This limitation is especially problematic in an environment were inference is present. The presence of interference can degrade the performance of such AM systems significantly. Such degradation can render the wireless transceiver useless or impractical in view of latency and robustness requirements.